The present invention relates to an overvoltage arrester, particularly for limiting overvoltages in low-voltage systems and for the lightning protected coupling of electrochemically separated circuits, the arrestor including at least one spark gap delimited between two spaced electrodes, an insulating member being disposed between facing surfaces of the spaced electrodes.
In such arrestors, which are disclosed, for example, in German Offenlegungsschrift [Laid-open Applications] Nos. 2,337,734 and 2,627,648, the electrodes are preferably planar, disc-shaped electrodes whose flat end faces are kept apart by the insulating layer, and the flashover, or arc-over, path is formed in the external region either between the cylindrical faces of the electrodes, or between the cylindrical face of the one electrode and the end face of the other electrode. The advantage of such an arrester is that the energy created during arc-over can be quickly dissipated and thus the danger of explosion is eliminated. Its drawback, however, is the not quite optimum quenching behavior for currents following flashover.
It has also been proposed, as described in German Application No. 2,934,236.7 and corresponding copending U.S. application Ser. No. 179,706 filed by us on Aug. 20, 1980 to have the region of spark discharge followed by a chamber whose walls contain an insulating material which emits a quenching gas, normally held in the insulating material, when under the influence of heat, the walls being provided with an exit opening through which the gases formed during the spark discharge can escape. Although this arrester is a significant improvement over the first-mentioned arrestor, its useful life is limited by the consumption of those electrode parts which form the arc-over point during firing or by consumption of the solid-phase gas insulating body.
It has furthermore been proposed, as disclosed in German Application No. 2,934,238.9, to provide an insulating layer containing a quenching gas in a spark gap whose point of arc-over is formed by the side faces of the electrodes, outside of an insulating layer provided to keep apart the electrode end faces. This design has also been found satisfactory but the above shortcomings apply here as well.